From Science Daily:
Just as members of an orchestra need a conductor to stay on tempo, neurons in the brain need well-timed waves of activity to organize memories across time. In the hippocampus — the brain’s memory center — temporal ordering of the neural code is important for building a mental map of where you’ve been, where you are, and where you are going. Published on May 30 in Nature Neuroscience, research from the RIKEN Brain Science Institute in Japan has pinpointed how the neurons that represent space in mice stay in time.
As a mouse navigates its environment, the central hippocampal area called CA1 relies on rhythmic waves of neural input from nearby brain regions to produce an updated map of space. When researchers turned off the input from nearby hippocampal area CA3, the refreshed maps became jumbled. While mice could still do a simple navigation task, and signals from single neurons appeared to represent space accurately, the population level code, or ‘orchestra’ was out of time and contained errors. “The neural music didn’t change,” said senior author Thomas McHugh, “but by silencing CA3 input to CA1 in the hippocampus we got rid of the conductor.”
McHugh and co-author Steven Middleton accomplished this by genetically engineering mice to express a nerve toxin in CA3 that shut down the synaptic junctions between CA3 and other brain areas. The overall neuronal activity was preserved, but with synaptic communication effectively muted, they could measure the impact of removing CA3 input on the space map in…